Communication networks are becoming widely used for distributing both high and low speed data over varying distances. Typically, a communication network is comprised of a number of network elements (for example Nodes, switches, routers etc) that are connected to each other in a variety of configurations so as to form a unified communication network. The communication network may extend over a small area, such as a company wide network, or may cover large distances, such as in regional or nationwide networks. The nodes allow network clients to input data for transmission over the network and to receive data transmitted over the network from other locations. Thus, data may be added to, or dropped from the network at node locations, as the data flows from point to point throughout the network.
One problem associated with communication networks is the problem of protection switching. In one situation, protection switching involves the process of switching network traffic from one network transmission path to another in the event of a network failure.
In another protection switching technique, typically used in ring networks, the network traffic is transmitted over working and protection transmission paths that flow in different directions over the network to the same destination. In the event of a network failure, either the working or protection transmission path will be selected to deliver the network traffic to the network element at the final destination. To ensure uninterrupted (continuous) traffic flow a protection group (PG) is provisioned at each node where at least one working and at least one protection elements are presented at every node. FIG. 1 shows an example illustration of the protection group (PG) as defined in Provide Bridge Backbone Network with Traffic Engineering (PBB-TE, i.e. IEEE 802.1Qay) which has one work and one protect. Also, IEEE 802.1Qay defines two PGs are must i.e. one on source end and other on the destination end. Also, the work (protect) entity is bi-directional and path should be congruent between the two PGs.
FIG. 2 shows the working mechanism of protection group (PG) in a topology as discussed in FIG. 1. In FIG. 2, where one or more nodes are connected to form an individual segment. Each node is provisioned to check for the fault in their individual segment or the whole segment connecting N1 to N5 with intermediate nodes N2, N3 and N4. Considering the fault has occurred between nodes N2 and N3. Since, all the nodes are provisioned to protection group, the (inner) work segment between the nodes N2 and N3 fails, the node N2 switches the traffic to node N6 which is the protect segment between the nodes N2 and N3.
Node 1 also switches the traffic to node N7 to reach node N5 as (outer) work segment also flows through the same link N2 and N3 thereby encountering fault and hence no continuity check message corresponding to (outer) work segment of the nodes N1 to N5. Since inner protection group between N2 and N3 would have protected the traffic over inner protect and simultaneously outer protection group between N1 and N5 would have protected the traffic over node N7 which leads to double protection. Also, the coordination issue arises wherein the inner protection group has to send information about the fault to the outer protection group and request for a pause while taking the action at the inner level. Such coordinations are bandwidth consuming and are not easy to implement in existing nodes. Timer based methods where protection switching times in inner protection group is considerably smaller than protection switching times in outer protection group would increase the overall protection switching time of the network.
Therefore, it would be desirable to have a system to perform protection switching in a communication network to overcome the above restrictions.